Bridle



0. A. mouuz June 25, 1968 BRIDLE Filed Dec; 27, 1965 IN VENTOR. DAVID A. MOI. INE

United States Patent 3,389,591 BRIDLE David A. Moline, Hamilton, Ontario, Canada, assignor to The Steel Company of Canada, Limited, Hamilton, 0ntario, Canada, a Canadian company Filed Dec. 27, 1965, Ser. No. 516,551 3 Claims. (Cl. 72-205) ABSTRACT OF THE DISCLOSURE An improved method and apparatus for use in a line in which strip travels longitudinally between a pair of line components and such method and apparatus dividing the strip extending between the components into first and second strip portions having differential tensions therein.

The invention resides in providing of a pair of rolls in engagement with the strip extending between the line components and applying a torque to one of such rolls to develop a differential between the tension in the first strip portion and the tension in the second strip portion. The strip is pinched between the rolls of said roll pair and the magnitude of pinching force exerted by the rolls is a function of the differential tension between that existing in the first strip portion and that existing in the second strip portion.

This invention relates to bridles for use in controlling tension in strip and is particularly directed to an improved bridle apparatus for altering strip tensions in continuous strip processing lines.

It is essential in the operation of most continuous high speed strip processing lines to alter strip tension at various stages of the process. For example, it may be essential in one continuous operation to reduce or obviate strip tension at a furnace or loop pit or in an annealing line and then necessary to immediately increase strip tension for improved sequential tracking through a series of equipment or for coiling and the like. Pinch roll units, multiple roll units and the like bridle apparatuses have been successfully employed for altering strip tension. Pinch roll units, being restricted by the amount of load which each unit can impart or take from the strip, necessitate a plurality of pinch roll units arranged in series where substantial tension changes are to be effected. Multiple roll bridle units, having a plurality of cascaded rolls, are arranged in a complex system for maximum wrap effect. Both units require a series of balanced, synchronous prime movers or braking devices to control roll torque because of the necessity for a substantially uniform roll peripheral velocity matched to the strip speed. Initial capital expenditures, especially for the latter unit, are high and uniform control of strip tensions difiicult to maintain.

It is normally desirable in the processing of strip to produce and maintain a smooth surface finish suitable for subsequent use and for processing such as, for example, in the production of steel strip for tin plating. A smooth strip surface provides a low friction coeflicient with resulting slippage and strip marking at pinch roll or multiple roll bridles or a low amplification factor with attendant poor tracking characteristics.

The operation of the above bridle units in altering strip tensions is a direct function of the coefficient of friction between the strip and rolls and the angle of wrap therebetween, the load or torque input or output in controlling strip tension and the amplification factor thus normally being readily predetermined in the design of these units.

3,389,591 Patented June 25, 1968 We have discovered a novel apparatus which departs in principle from conventional bridle design and which permits effective strip tension control with a surprisingly high amplification factor out of proportion to the coefficient of friction and angle of wrap.

It is a principal object of the present invention, therefore, to provide a bridle apparatus for improved control of strip tension with a high amplification factor.

It is another object of the invention to provide a bridle apparatus which obviates slippage and marking of the strip and maintains a smooth surface finish with optimum strip tracking control.

Another object of the present invention is the provision of a bridle apparatus having means for sharing and balancing roll torque requirements for each roll drive; thus avoiding normal synchronization and power distribution difficulties inherent in conventional bridle systems.

And another object of the present invention is the provision of a bridle apparatus which is simple and inexpensive in construction and reliable and trouble-free in operation.

These and other objects of the invention and the manner in which they can be attained will become apparent from the following detailed description of the drawings, in which:

FIGURE 1 is a perspective view generally illustrating the apparatus of the present invention;

FIGURE 2 is a schematic illustration showing the basic roll configuration of the apparatus of the invention having a pair of ancillary strip deflector rolls;

FIGURE 3 is a vertical section taken through an embodiment of the apparatus of the present invention illustrated in FIGURE 2 having means incorporated therein for measuring input and output strip tension; and

FIGURE 4 is an end elevation of still another embodiment of the invention.

Like reference characters refer to like parts throughout the description of the drawings.

With particular reference to FIGURE 1 of the drawings, the apparatus of the invention comprises a pair of opposed rolls 10, 11 journalled for rotational movement in bearing blocks 12, 13 and each independently coupled at one end to a prime mover or braking unit such as motors 14, 15 through gear reducers 16, 17. A floating, idler roll 19 is disposed between and parallel to rolls 10, 11 to one side of the plane joining the axes of the two said rolls adjacent the roll gap 18 defined by the two said opposed rolls. Rolls 10, 11 preferably are of the same diameter and are adapted to have the same peripheral speed. Roll 19 is of a diameter normally smaller than rolls -10, 11 but of a minimum diameter primarily dependent on the strip thickness for reasons which will become apparent as the description proceeds. Strip material 23 such as strip steel is wrapped substantially about floating roll 19 entering and departing through gap 18 and passing between rolls 10, 19 and 19, 11.

With reference now to FIGURE 2, which shows the roll configuration of a typical application of the present invention to a strip processing line, strip 23 at entry to and exit from the apparatus is passed over and around deflector rolls 20, 21 journalled for free-running rotational movement in proximity to and parallel to rolls 10, 11 for the provision of a substantial angle of Wrap of the strip 23 around said rolls 10, 11.

In operation, the tension under which strip 23 is normally maintained snugs floating roll 19 against rolls 10,

o 11 causing the pressures P P to be applied to the strip at the bearing surfaces between rolls 10, 19 and 19, 11 and providing an effective double pinch to the strip. The pressures P P applied to the strip by the floating roll 19 and countered by the opposed rolls 10, 11 are directly proportional to the tension differential between the tension of the strip entering and departing from the unit and are uniformly distributed over the full width of the strip in contact therewith. The direct abutment of floating roll 19 with the strip between said roll and rolls 10, 11 ensures substantial even torque sharing between the two opposed rolls and their respective drive motors 14, 15 which may be functioning to drive or retard the rotation of said rolls.

The spacing of the axes of the opposed rolls defining the roll gap width relative to the diameter of a floating roll determines the resolution of force vectors and effective pressures P P brought to bear on the strip. The angles at defined by the lines drawn through the centers of rolls 10, 19 and 19, 11 respectively and the line drawn through the centers of rolls 10, 11 is a measure of the resolution of forces bearing on the strip, and thus the amplification factor of the unit. The angles 0: thus defined, for a given set of roll diameters, depend upon the spacing of the axes of the opposed rolls. A wider spacing of the opposed rolls, with a corresponding smaller angle 0:, providing a large force resolution and high amplification factor, is critical in the lower limits of angle a in that the resolved forces P and P are high for a moderate tension difference. The upper limit of angle a effected by a closer spacing of the opposed rolls, providing a relatively small force resolution, is not critical and is governed by practical considerations which include the relative size of the rolls and the amplification factor desired. It is desirable to have a floating roll smaller in diameter and lighter in construction than the opposed rolls, the critical minimum diameter of the roll being governed by the strip thickness. The floating roll diameter thus is larger than that critical diameter which will bend and work the strip as it travels around the roll producing plastic deformation and size reduction.

In the operation of this embodiment, strip 23 is directed by roll 20 from a source of strip to the periphery of roll 10, passes through roll gap 18, and is wrapped about roll 19, returns through roll gap 18, travels about the periphery of roll 11, and is directed by deflector roll 21 to the next stage of the process. Floating roll 19 is at all times free to rotate in proximity to gap 18 by contact through the moving strip with the opposed rolls 10, 11. If it is desired to increase the tension of the strip, prime movers such as motors, operably connected to rolls 10, 11 illustrated in FIGURE 1 impart torque to said rolls at the desired peripheral roll speed matched to the strip line speed. If it is desired to reduce the tension of the strip, rolls 10, 11 can be connected to braking devices I such as motors operated in reverse which impart a negative torque to the rolls which effectively reduces the strip tension.

With reference now to FIGURE 3, wherein the installation corresponds to the arrangement of parts shown in FIGURE 2, a pair of deflector rolls 26, 27 are positioned in series relative to driven rolls 28, 29 respectively to provide maximum wrap about said driven rolls and to deflect the strip relative to pressure-indicating rolls 30, 31 respectively which are operatively connected to transducers for measuring the tension differential in the strip. Rolls 28, 29 are each journalled at one end in bearing blocks 32, 33 and at the opposite end to gear reducing means, not shown, operatively connected to prime movers. Floating roll 34 is journalled at each end in bearing blocks 35 adjustably mounted on frame 36 for movement towards and away from roll gap 37. Rolls 26, 27 are journalled at each end in bearing blocks 38, 39 and rolls 30, 31 "are journalled at each end in bearing blocks 40, 4-1. This embodiment operates in the manner described with reference to FIGURE 2 above.

FIGURE 4 illustrates another embodiment of the present invention wherein three driven rolls 43, 44 and 45 have floating rolls 46 and 47 disposed adjacent the two roll gaps 48, 49; strip 50 passing through the system for tension control in the manner described hereinabove with reference to the embodiments of the invention illustrated in FIGURES 1 to 3.

The present invention provides a number of important advantages. A high amplification factor can be provided by a simple and inexpensive apparatus thus effectively altering strip tension. Improved tracking characteristics are imparted to the strip with slippage and marking substantially obviated. The motors for driving or retarding the rolls can be readily synchronized and balanced as to torque input or output, as desired. The bridle units can be readily installed in existing strip processing lines requiring a small amount of floor space and a minimum of conversion time and expense.

It will be understood, of course, that modifications can be made in the preferred embodiments of the invention described and illustrated herein without departing from the scope and purview of the invention as defined by the appended claims.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. A bridle for use in a line wherein strip travels longitudinally between a pair of line components and wherein such bridle is interposed between said components in engagement with the strip extending therebetween to divide such extending strip into first and second strip portions having differential tensions therein, the improvement comprising a pair of rotatably mounted rolls in side-by-side parallel relation and spaced to provide a gap therebetween, said strip forming a loop between said rolls and being wrapped about substantial portions of their peripheries,

an intermediate roll disposed in said strip loop and positioned to pinch the strip between itself and respective rolls of said roll pair,

and means for applying a torque to the rolls of said roll pair exclusively to develop differential tensions in said first and second strip portions.

2. For use in a line wherein strip travels longitudinally between a pair of line components, the method of dividing the strip portion extending between the line components into first and second strip portions having differential tensions therein, which comprises passing the strip portion intermediate the line components through a pass formed by a pair of rolls disposed in side-by-side parallel relation,

pinching the strip between the rolls aforesaid to minimize slippage between the rolls and the strip,

applying a torque to one of the rolls to develop a differential between the tension in the first strip portion and the tension in the second strip portion, and translating an increase or decrease in differential tension between that existing in the first strip portion and that existing in the second strip portion to an increase or decrease respectively of the magnitude of pinching force exerted by the rolls on the strip.

3. For use in a line wherein strip travels longitudinally between a pair of line components, the method of dividing the strip portion extending between the components into first and second strip portions having differential tensions therein, which comprises passing the strip portion intermediate the line components successively about substantial portions of the peripheries of a set of three rolls disposed in side-by-side parallel relation,

pinching the strip between the first roll and the second roll and between the latter and the third roll to minimize slippage between the rolls and the strip,

applying torque to the first and third rolls of the roll and translating an increase or decrease in diife'rential r tension between that existing in the first strip portion and that existing in the second strip portion to an increase or decrease respectively of the magnitude of pinching force exerted by the rolls on the strip.

6 References Cited UNITED STATES PATENTS 2,291,361 7/1942 Walsh 72-205 3,171,464 3/1965 Holtz 72-160 3,253,445 5/1966 Franek 72-205 CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner. 

